Scientists Seek to Prove Link Between Amazon Gold Mining and Disabilities in Children

Deep in the Amazon, Indigenous women say they now fear becoming pregnant.

The rivers that once sustained their people have become tainted with mercury from illegal gold mining, posing serious risks to their unborn children.

“Breast milk is no longer safe,” said Alessandra Korap, a leader of the Munduruku people.

In Sai Cinza, a Munduruku community surrounded by illegal mines, the family of three-year-old Rany Ketlen is struggling to understand why she has never been able to lift her head and suffers from frequent muscle spasms.

Scientists may soon have an answer. Preliminary data from a new study on mercury contamination suggest that Rany is one of at least 36 people in the region, most of them children, who show signs of neurological disorders that cannot be explained by genetics.

While researchers have long warned of the dangers mercury poses to Indigenous children in the Amazon, no one has yet been able to scientifically prove a direct link between contamination and disabilities within affected communities — something this new study aims to establish.

“Eat the poisoned fish or go hungry”

Rany’s father, Rosilton Saw, followed in the footsteps of his own father, Rosenildo, working for years as a small-scale gold miner near their village.

Sitting in their modest one-room wooden home, the elder Saw admitted he knew mercury was dangerous, but said the small amount of gold they extracted — about 30 grams a week — was just enough “to make ends meet.”

The family regularly eats surubim, a carnivorous fish known to accumulate mercury in its tissues. Because Rany struggles to swallow, she is fed fish soup instead.

In recent years, local health authorities have reported dozens of similar cases across the wider region. But limited access to medical testing and healthcare has made it difficult to fully grasp the scale of the crisis or pinpoint its exact causes.

Now, researchers are collecting data on neurological symptoms linked to mercury poisoning — ranging from severe brain damage to memory loss. The long-term study is expected to conclude in late 2026.

Supported by Brazil’s leading public health institute, Fiocruz, scientists believe that mercury is leaking into waterways after being used by miners to bind small gold particles — a largely unregulated practice that has surged amid record-high gold prices.

Mercury has contaminated the fish that are a dietary staple for Indigenous communities and has been detected at dangerously high levels in women’s placentas, breast milk, and children, often two to three times above what is considered safe for pregnant mothers.

Chief Zildomer Munduruku, a nurse, said that despite official warnings, he cannot ask his people to stop eating fish.

“If we follow those rules,” he said, “we’ll starve.”

Even if mining stops, mercury will remain

Far from Sai Cinza, world leaders will gather next month in the Amazon for the UN Climate Summit (COP30) — dubbed the “Forest COP” — which aims to highlight threats to tropical rainforests and their inhabitants, including illegal mining.

Since returning to office in 2023, Brazilian President Luiz Inácio Lula da Silva has expelled thousands of miners from Indigenous territories. But the mercury they left behind continues to circulate through air, water, and soil, creating a long-term public health crisis.

In a statement, Brazil’s Health Ministry said it has expanded mercury monitoring in Munduruku territory, trained local health workers to recognize early signs of poisoning, and invested in clean water sources for remote communities.

Fiocruz researcher Paulo Basta, who has studied mercury contamination among Indigenous peoples for over three decades, warned:
“Even if gold mining in the Amazon were completely shut down, the mercury that has already accumulated will persist for decades.”

Research reviewed by Reuters, along with new data and interviews, suggests that the humanitarian crisis caused by illegal mining will have lasting effects on current and future generations in the Amazon.

A 2021 study by Basta and his team found that 10 out of 15 mothers tested in three Munduruku villages had elevated mercury levels. Another study found that in one Yanomami village with intensive mining, 12 of 13 people had dangerously high levels in their bloodstream. By March 2025, nearly all 546 registered cases in the government’s database had been documented by Basta’s team.

“This is just the beginning,” he said. “Thousands more Munduruku, Yanomami, and Kayapó may already be affected.”

Proving the cause is not easy

The current Fiocruz study aims to fill a critical missing link — proof that mercury exposure causes disabilities. Researchers are tracking 176 pregnant women to test their children during the first years of life.

In Sai Cinza, early data show that average mercury levels in mothers were five times higher than what Brazil’s Health Ministry considers safe, while their children’s levels were three times higher. Rany’s one-year-old sister, Railyne, is among the infants being monitored, though she has not yet shown symptoms.

“This mercury disease — if you don’t look for it, you won’t find it,” said Clediane Carvalho, a nurse who first connected researchers with sick Indigenous children years ago. She fears that without such studies, the crisis will be “buried and forgotten forever.”

Yet proving causation remains a major challenge.

Fiocruz researchers note that Indigenous communities often lack access to basic healthcare and are vulnerable to infectious diseases, which can also cause neurological problems. Inbreeding, common in small, isolated populations, may lead to genetic disorders that complicate diagnosis.

Fernando Kok, a geneticist at the University of São Paulo working on the Fiocruz study, said mercury is likely one of several contributing factors among the 36 patients without identifiable genetic disorders — but it may not be the only one.

Tests that detect mercury in the body offer only a snapshot of recent exposure, he explained, making it nearly impossible to link contamination directly to earlier brain damage.

“It’s a perfect crime,” Kok said, “because it leaves no trace.”